Polyamides represented by polyamide 6 and polyamide 66 (hereinafter, sometimes abbreviated as “PA6” and “PA66” respectively) or the like have excellent fabricability, mechanical properties, and chemical resistance. Therefore, the polyamides are widely used as a material for various parts, such as for automobiles, electric and electronic parts, industrial materials, engineering materials, and daily and household articles.
In the automobile industry, as an environmental measure, there is a need to lighten the weight of the automobile body in order to reduce exhaust gases. To respond to this need, the polyamides are increasingly used as exterior materials and interior materials or the like for the automobiles, instead of metals. The level of the properties required for the polyamides used as the exterior materials and interior materials or the like for the automobiles, such as heat resistance, strength, and surface appearance, is further increased.
Of these, since the temperature in an engine room tends to increase, the need to increase the heat resistance of a polyamide used for materials in the engine room is growing stronger.
In the electric and electronics industry, such as household appliances, lead-free surface-mount (SMT) solder is advanced. There is a need for increased heat resistance for the polyamide which is used as materials for the household appliances or the like, and can withstand the increased melting point of the solder caused by the lead-free of the solder.
On the one hand, the polyamides such as PA6 and PA66 cannot satisfy these requirements in terms of heat resistance, since their melting point is low.
To resolve the above-described problems with conventional polyamides such as PA6 and PA66, a high-melting-point polyamide has been proposed. Specifically, a polyamide (hereinafter, sometimes abbreviated as “PA6T”) formed from terephthalic acid and hexamethylenediamine has been proposed.
However, the PA6T is a high-melting-point polyamide having a melting point of about 370° C. Therefore, even if a molded article is obtained from the PA6T by melt molding, pyrolysis of the polyamide is severe, which makes it difficult to obtain a molded article having sufficient properties.
To resolve the above-described problem with the PA6T, a high-melting-point semi-aromatic polyamide (hereinafter, sometimes abbreviated as “a 6T-based copolymer polyamide”) or the like having terephthalic acid and hexamethylenediamine as main components has been proposed. This high-melting-point semi-aromatic polyamide is obtained by copolymerizing an aliphatic polyamide, such as PA6 and PA66, or an amorphous aromatic polyamide (hereinafter, sometimes abbreviated as “PA6I”) formed from isophthalic acid and hexamethylenediamine, or the like with the PA6T, and has a melting point lowered to about 220 to 340° C.
As the 6T-based copolymer polyamide, Patent Literature 1 discloses an aromatic polyamide (hereinafter, sometimes abbreviated as “PA6T/2MPDT”) which is formed from an aromatic dicarboxylic acid and an aliphatic diamine, in which the aliphatic diamine is a mixture of hexamethylenediamine and 2-methylpentamethylenediamine.
In contrast to an aromatic polyamide formed from an aromatic dicarboxylic acid and an aliphatic diamine, a high-melting-point aliphatic polyamide (hereinafter, sometimes abbreviated as “PA46”) formed from adipic acid and tetramethylenediamine, and an alicyclic polyamide formed from an alicyclic dicarboxylic acid and an aliphatic diamine, or the like have been proposed.
Patent Literatures 2 and 3 disclose a semi-alicyclic polyamide (hereinafter, sometimes abbreviated as “PA6C copolymer polyamide”) formed from an alicyclic polyamide (hereinafter, sometimes abbreviated as “PA6C”) formed from 1,4-cyclohexanedicarboxylic acid and hexamethylenediamine, and another polyamide.
Patent Literature 2 discloses that electric and electronic members formed from a semi-alicyclic polyamide blended with 1 to 40% of 1,4-cyclohexanedicarboxylic acid as a dicarboxylic acid unit have heat resistance which can resist a temperature under solder conditions.
Patent Literature 3 discloses that automobile parts produced from a polyamide composition substantially consisting of a unit derived from an aliphatic dicarboxylic acid and an aliphatic diamine have excellent fluidity and toughness or the like.
Patent Literature 4 discloses that a polyamide formed from a dicarboxylic acid unit containing 1,4-cyclohexanedicarboxylic acid and a diamine unit containing 2-methyl-1,8-octanediamine has excellent light resistance, toughness, moldability, low weight, and heat resistance or the like. As a production method for the polyamide, Patent Literature 4 discloses that a polyamide having a melting point of 311° C. is produced by reacting 1,4-cyclohexanedicarboxylic acid and 1,9-nonanediamine at 230° C. or less to produce a prepolymer, which is then subjected to solid phase polymerization at 230° C.
Patent Literature 5 discloses that a polyamide using 1,4-cyclohexanedicarboxylic acid having a trans/cis ratio of from 50/50 to 97/3 as a raw material has excellent heat resistance, low water absorbance, and light resistance or the like.
Patent Literature 6 discloses a polyamide formed by polymerizing 1,4-cyclohexanedicarboxylic acid and a diamine having a substituent branched from a main chain.
Patent Literature 7 discloses a polyamide formed by polymerizing 1,4-cyclohexanedicarboxylic acid, undecamethylenediamine, and 1,6-diaminohexane.
Patent Literature 8 discloses a polyamide formed by polymerizing 1,4-cyclohexanedicarboxylic acid, 1,12-diaminododecane, and 1,6-diaminohexane.
Patent Literature 9 discloses a copolymer polyamide formed by polymerizing an alicyclic dicarboxylic acid, a diamine, and a predetermined copolymer component.